1. Field of the Invention
The present invention relates to a method of compressing a color reproduction range in creating a color profile used for color matching of a color image forming device.
2. Description of the Related Art
The electrophotographic recording type printer (image forming device) that forms images on a recording medium such as paper by using color toners of Cyan, Magenta, Yellow, and Black adopts the subtractive color mixing as the principle of color reproduction, in which the color tones absorb the reflected light from the recording medium to develop a color. In general, the color reproduction range in an output device such as an image forming device (hereinafter, referred to as the “printer color reproduction range”) tends to be narrower than the color reproduction range in an input device such as a monitor that adopts the additive color mixing as the principle of color reproduction, in which spontaneous light develops a color.
Because of the above, a number of technologies referred to as gamut mapping are proposed, in which colors that cannot be represented by an image forming device are compressed to a color reproduction range that can be represented by the image forming device.
As the most primitive technique thereof, there is a method in which colors in a color reproduction range to be mapped (hereinafter, referred to as the “source color reproduction range”) are compressed in the direction of saturation while preserving the brightness and hue and mapped to the printer color reproduction range in the Lab color space represented by the brightness, saturation, and hue and perceptually uniform. There is also a technique in which colors in the source color reproduction range are compressed toward a virtual convergent point provided inside of the printer color reproduction range and mapped to the printer color reproduction range.
Furthermore, a technique that is an improved primitive technique is also proposed. For example, a technique is proposed in which a method of compressing colors in the saturation direction while preserving the brightness and hue and a method of compressing colors toward the virtual convergent point provided inside of the printer color reproduction range are switched in accordance with the brightness of the colors in the source color reproduction range on the Lab color space (see Japanese Patent Laid-Open No. 2001-257900).
In addition, there is also proposed a technology for performing gamut mapping by variously setting virtual convergent points within the printer color reproduction range in accordance with the position of the color in the source color reproduction range on the Lab color space (see Japanese Patent Laid-Open No. H09-098298 (1997)).
The technologies described in Japanese Patent Laid-Open No. 2001-257900 and Japanese Patent Laid-Open No. H09-098298(1997) are those that determine the mapping direction from the source color reproduction range to the printer color reproduction range, based on the geometric rules on the uniform color space such as the Lab color space, and a number of technologies other than those described above are proposed.
However, the geometric rules disclosed in Japanese Patent Laid-Open No. 2001-257900 and Japanese Patent Laid-Open No. H09-098298(1997) are determined by extending the correspondence relationship between the source color reproduction range and the printer color reproduction range defined as to a comparably small number of colors, for example, YMCKRGB, into a large region. Consequently, it is not necessarily possible to appropriately define the correspondence relationship as to colors other than those regarded as important when determining rules.
Furthermore, in many cases, the geometric rules are determined after the uniform color space represented three-dimensionally is degenerated to a two-dimensional plane. Because of this, for example, even in a case where it is appropriate to map a color existing on a certain hue plane in the source color reproduction range to a color existing on another hue plane in the printer color reproduction range, such mapping cannot be implemented.
Moreover, when trying to solve the problems as described above by introducing various rules, there newly occurs such a problem in which the rule design becomes too complicated.